#include<stdio.h>
#include<math.h>

int main(void)
{
	double x1,x2,x3,y1,y2,y3,a,b,c,d,s;
	scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
	a=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	b=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
	c=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
	
	if(a+b>c&&a+c>b&&b+c>a)
	{
		d=(a+b+c)/2;
		s=sqrt(d*(d-a)*(d-b)*(d-c));
		printf("%.2lf",s);
	}
	else
	{
		printf("No answer");
	}
	
	return 0;
}
